One of my favorite homebrew games on the PSP, CS PSP brings the counter-strike fun in a 2d bird's eye view type gameplay.
CS PSP has online play and you can even make your own servers. A lot of people play this game online so you can expect to play against other people.
You can also type text while you play. The game has just released it's latest version 1.6.

I find myself playing this game daily. A VERY addicting game, PSP revolution will keep you hooked.
Based on DDR, you use the D-pad and the Circle, Square, Triangle and Cross buttons to hit the notes.
The best feature about this homebrew is that it is very customizable.
Just search for a song in the search bar. Download the simfile and put it into the SONGS folder in the application.
The game has just been updated to version 0.4

Winner of the PSP-Hacks Homebrew Idol 2008 contest, stakker delivers simplistic and addictive gameplay
The goal is to build up a tower of blocks and knock it down for points. It may sound wierd, but don't judge it until you try it!
You can also listen to your own music while you play, just make sure your music is in ms0:/PSP/MUSIC and your set.

Want to play GBA games on your PSP? Now you can with GPSP and GPSP Kai.
GPSP can emulate gba games at full speed! A very impressive emulator. Pretty much all games work for it.
GPSP is for PHAT PSP's and GPSP KAI is for SLIM PSP's. For phat psp users, put gpsp into your GAME150 folderNote: You will need a gba BIOS file to use the emulator, I cannot provide you with one. However, google is your friend
The links below contain the latest versions.

SNES emulation on the PSP has come a long way. This latest version Snes9xTYLsmcm Test 5 27/05/08 works the best.
At the moment, Chrono Trigger can be played full speed (The intro kind of lags.. but the gameplay is perfect)
SMRPG is turning out great, but still pretty slow. The other snes games work fabulously.
Check out this emulator to play some snes classics!

A long time ago, I had my pokemon crystal game stolen. You can imagine my joy when I heard of a gameboy color emulator for the PSP.
Rin allows you to play the original gameboy games and gameboy color games on your PSP.
The emulator emulates the games at full speed.

PSP-hack's own Psimxc has been very hard at work fixing and tuning up PSPtube.
his releases are frequent and amazing, and right now he has 2 versions
1 PSPtube version contains only youtube and is very fast
the other version contains many video streaming sites in 1 application, It is called Super PSPtube.
Once again, I'd like to thank Psimxc for his hard work. Definitely check out PSPtube!*Password for Super PSPtube is psimxc_is_my_pimp

FOR PSP SLIM OWNERS ONLY
The description on the FuSa website (http://foosa.do.am/) has a great description:

As you know, sony doesn't allow to use interlaced mode while playing games.
It's mean, that all users of SDTV (standard definition TV) aren't able to play their favourite games on TV screen :(
But even if your TV supports progressive scan (aka HDTV), the picture will be not fullscreen.

This's holy sh*t! Let's get rid of this f*ckin limitations with FuSa!

That's right, you can play your games and homebrew on your TV in fullscreen!
The project is still in the works, but it works great. It may be a little slow but they're going to fix that in future updates.

PSP-hacks very own Blade_Punk has created a drum kit simulator.
This homebrew application will allow you to play the drums on the PSP
The newest update includes a guitar simulator and composer. This update has made Vdrum into Rock station.

The most popular shell for the PSP. iRshell allows your to launch your homebrew, UMD's and ISO's in 1 template.
It also allows you to play your music in the background to your homebrew and games.
It can be used as a remote. There are tons of functions for this application,
you can read it all here: http://irshell.org/wikishell/index.p...hy_iR_Shell%3F